In an announcement earlier this year, the group said, “It <a href="http://www.alankerrleisure.co.uk/Nike-Air-Max-90-Womens-c-22_24.html" title="Nike Air Max 90 Womens">Nike Air Max 90 Womens</a> is clear that some forms of technology would provide an athlete with assistance that runs contrary to the values of the sport.” It has since appointed a technical <a href="http://www.alankerrleisure.co.uk/Nike-Air-Pegasus-83-Womens-c-52_54.html" title="Nike Air Pegasus 83 Womens">Nike Air Pegasus 83 Womens</a> committee to study the shoe question, and to make a report with recommendations. (The report was originally intended to be <a href="http://www.carlosvisuara.es/Nike-Blazer-Low-Mujer-c-52_54.html" title="Nike Blazer Low Mujer">Nike Blazer Low Mujer</a> released to the public by the end of the year; it will now reportedly <a href="http://www.aralys.fr/Nike-Air-Vapormax-Femme-c-62_63.html" title="Nike Air Vapormax Femme">Nike Air Vapormax Femme</a> be released in 2020.)When we asked Nike last year about whether its shoes might violate I.A.A.F. rules, a spokesman said the shoe “meets all I.A.A.F. <a href="http://www.jonhaylett.co.uk/Nike-Air-Max-90-Womens-Pink-c-13_17.html" title="Nike Air Max 90 Womens Pink">Nike Air Max 90 Womens Pink</a> product requirements and does not require any special inspection or approval.”On Thursday, the company said in a statement, “We respect the I.A.A.F. and the spirit of their <a href="http://www.annieemmerson.co.uk" title="www.annieemmerson.co.uk">www.annieemmerson.co.uk</a> rules, and we do not create any <a href="http://www.anamartinez.es/Nike-Air-Presto-Mujer-c-76_78.html" title="Nike Air Presto Mujer">Nike Air Presto Mujer</a> running shoes that return more energy than the runner expends.”

There is no such thing as a large-scale randomized control trial for marathons <a href="http://www.carlosvisuara.es/Adidas-NMD-Mujer-c-67_69.html" title="Adidas NMD Mujer">Adidas NMD Mujer</a> and shoes, but there is Strava, a fitness app that calls itself the social network for athletes. Nearly each weekend, thousands of runners compete in races, <a href="http://www.dancardwell.co.uk/Nike-Air-Odyssey-Womens-Mens-c-36_37.html" title="Nike Air Odyssey Womens Mens">Nike Air Odyssey Womens Mens</a> record their performance data on satellite watches or smartphones, and upload their race data to the app. This data <a href="http://www.aazmotos.fr/Nike-Air-Span-2-Femme-c-25_26.html" title="Nike Air Span 2 Femme">Nike Air Span 2 Femme</a> includes things like a race name, finish time, per-mile splits and overall <a href="http://www.carlosvisuara.es/Adidas-ZX-Flux-Mujer-c-82_84.html" title="Adidas ZX Flux Mujer">Adidas ZX Flux Mujer</a> elevation profile. And about one in four races includes self-reported information about a runner’s shoes.In all, this data includes race results from <a href="http://www.aralys.fr/Nike-Air-Max-90-Homme-c-19_27.html" title="Nike Air Max 90 Homme">Nike Air Max 90 Homme</a> about 577,000 marathons and 496,000 half marathons in dozens of countries from April 2014 to December 2019.These approaches are essentially identical to the ones The Times <a href="http://www.beverleyely.com/Nike-Air-Max-Classic-BW-Womens-c-31_32.html" title="Nike Air Max Classic BW Womens">Nike Air Max Classic BW Womens</a> used last summer. See that article for more <a href="http://www.emilytorino.it/Nike-Air-Max-95-Donne-c-46_47.html" title="Nike Air Max 95 Donne">Nike Air Max 95 Donne</a> examples and methodological details.

We measured the shoes’ performance using four different methods — each with its own strengths and <a href="http://www.romanvavrik.cz/Nike-Air-Vapormax-D&225;msk&233;-c-55_56.html" title="Nike Air Vapormax Dámské">Nike Air Vapormax Dámské</a> flaws:None of these approaches are perfect, but they all point to the same conclusion: Something is happening in races with the Vaporfly and Nike Next% shoes <a href="http://www.prestamatic.fr/Nike-Air-Max-2017-Femme-c-13_14.html" title="Nike Air Max 2017 Femme">Nike Air Max 2017 Femme</a> that is not happening with most any other kind of popular shoe.More than 110,000 athletes uploaded data for <a href="http://www.raheembakare.co.uk/Nike-Air-Max-Thea-Womens-c-43_45.html" title="Nike Air Max Thea Womens">Nike Air Max Thea Womens</a> more than one marathon, and about 47,000 uploaded data for three or more marathons. The <a href="http://www.jonhaylett.co.uk/Nike-Air-Presto-Womens-c-33_35.html" title="Nike Air Presto Womens">Nike Air Presto Womens</a> Strava data allows us to follow these repeat racers over time and as they change shoes.